tools: free select tool fill option
provoked by #10388, and I was getting tired of blocking in areas with a brush and started using the free select Tool.
This merge adds a 'Fill selection' checkbox to the selection options, visible only on the Free Select tool.
When checked, a committed selection will be filled with the current context FG color. This enhances the Free Select Tool, allowing a quicker way to draw blocks of color.
Edited by Mark Sweeney